As a file organizational issue, you want photos in one area of your computer's hard disk, and separately, you keep the catalog somewhere else — just so they are separate entities and relatively easy to find. From a performance point of view, if you have multiple disks, you want the catalog to be on your fastest disk and the photos to be on your slowest disk. Also, in my opinion, especially if you are a beginner, you want to put all photos in a single catalog, anything else will cause unnecessary effort, unnecessary confusion and unnecessary disorganization (yes dis-organization)

Inside a catalog, you can segregate different types of photos by keywords, or by collections, or by folders, or by color labels (if you have only a few categories) or a combination of these. I prefer keywords.